[time-nuts] TAPR TICC boxed

Attila Kinali attila at kinali.ch
Mon Apr 3 05:22:14 EDT 2017


On Mon, 3 Apr 2017 15:05:55 +1200 (NZST)
Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:

> For even more fun you could try to detect the PTFE phase change  at around 20C using a cable with PTFE dielectric.

This will require several 100 meters of cable to be measureable with
the TICC. Modern cables are all <500ppm/K, good cables <10ppm/K, phase
stable cables reach even <1ppm/K. Measuring a change of 10ppm with
a resolution of 60ps means that the delay has to be in the order of 6┬Ás,
which is close to 1000m of cable. Even if dithering gives another facor
of 10, this still means 100m of cable. 

For this level of comparison I would suggest to use a sinusoidal signal,
instead of a pulse, and do phase comparison, which gives a resolution
in the order of 1ps with very little effort, thus reducing the required
cable length to 10-20 meters.


			Attila Kinali

[1] "Temperature Stability of Coaxial Cables", Czuba and Sikora, 2011
http://przyrbwn.icm.edu.pl/APP/PDF/119/a119z4p17.pdf

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